Mechanism of Formation of the Protective Films on Steel by Volatile Compounds of Rapeseed Cake

Abstract

The mechanism of formation of protective films on the steel surface in the course of its treatment by the extract of rapeseed (Brassicaceae family) cake regarded as a volatile corrosion inhibitor and its compo- nent composition are experimentally determined and theoretically substantiated. The dynamics of changes in the component composition of volatile compounds in the 2-propanol extract of rapeseed cake is studied by the methods of gas chromatography, mass spectrometry, and IR-spectroscopy. The influ- ence of individual components on the corrosion behavior of steel under the conditions of periodic con- densation of atmospheric moisture is investigated. It is shown that the main components of the 2-propanol extract responsible for its anticorrosion efficiency are aldehydes, ketones, and glycosides. A model of the structure of protective films is proposed. In the course of transportation and conservation, metal products are damaged by corrosion, which decreases their user and export values. Hence, it is necessary to guarantee their temporary anticorrosion protection in or- der to preserve their quality and the outward appearance of the surfaces under the atmospheric conditions (1, 2). In this case, the most efficient and (sometimes) the only possible method for the protection of metals is given by the volatile inhibitors. At present, the production of volatile inhibitors of the atmospheric corrosion is absent in the Ukraine and the domestic market is filled with extremely expensive imported products, sometimes of very low quality. Due to the insufficient supply of these inhibitors, the increase in the cost of raw materials used for their pro- duction, and a permanent strengthening of the sanitary-hygienic requirements to the means of corrosion protec- tion, it is necessary to create new inhibiting compositions based on the natural resources. Thus, the organic compounds obtained from ecologically safe and annually renewed vegetable raw materials seem to be quite promising for the development of new volatile inhibitors of the atmospheric corrosion (3-6). In (7, 8), it is shown that the wastes of the production of oil from rape seeds (Brassicaceae family) may serve as a source of natural organic compounds. Moreover, the chemical compositions of the volatile compounds of 2-propanol extract of rapeseed cake and the inhibiting efficiency of this extract were investigated. However, we do not know the compounds appearing in the composition of this extract and responsible for its inhibiting effi- ciency. Therefore, it is necessary to study the specific features of the mechanism of formation of protective films formed from the vapors of the extract of rapeseed cake on the steel surface and to determine the compositions of these components.